1. Field of the Invention
The present invention relates to an image forming device that forms images by expanding image data into bitmap data.
2. Related Art
Various image forming devices are known in the art, such as a color laser printer. The color laser printer receives image data representing a color image from a host computer and divides the image data into a plurality of bands in one-page units. Then, the color laser printer expands the image data into bitmap data for each color in each band and prints the image onto paper based on the bitmap data.
To reduce the amount of memory required in such an image forming device, printing starts based on bitmap data that has already been expanded before all of the one-page worth of image data has been expanded into bitmap data. Therefore, if more time than that necessary for the expansion into bitmap data is required, then the bitmap data is interrupted during the printing, which leads to a problem called print overrun in which the printing onto the paper does not proceed normally.
A printer disclosed in Japanese Patent Application-Publication No. 2001-10123 proceeds expansion process for each color in parallel by dedicated color hard renderers and, in order to prevent print overruns, estimates the time required for the expansion process for each color in each band, and then modifies the expansion process that is allocated to the different hard renderers for each band, based on the estimated time.
In this printer, however, it is necessary to curtail the time required for the expansion process by reducing the resolution for each color if it is not possible to prevent the occurrence of a print overrun even by modifying the expansion process allocated to the hard renderers. In such a case, a problem occurs in that the appearance of a printed image is greatly degraded.